alchemy/herbalist

Transmute living steel (buy ghost iron ore/bars on the AH, transmute to trillium, transmute to living steel once per day). Sell on AH raw, or craft into belt buckles and sell (if you have a blacksmith).

Otherwise, sell flasks/elixirs/potions on the AH. Use spirits of harmony to buy golden lotus for this.

Beyond the 2 recipes you learn at 525 alch is purely discovery based, just go make your master health potions or alchemist's rejuvenation to learn more, and any discoveries you make are able to spawn more discoveries. Little random, but by the time you hit 600 you should have most everything.

As for motes of harmony there is no magic in it, just kill anything that moves in Pandaria. Mobs in the Vale of Eternal blossoms have the best droprate overall, but as a tank I favor doing my farming in Dread Wastes. The main reason for that is it is much easier to round up a horde of mantid and mow them down. The second reason is the powerful buffs available to you, allowing inflated survivability, damage and/or mobility.

I seem to have learnt all there is at the alchemy trainer but I'm not at the cap yet. Why is this?

Because you need to discover the few remaining recipes the trainer won't teach you by making some of the one's he has. All of the final few recipes in alchemy come from random discoveries when making Mists recipes.

I don't mean to sound cocky but the best and quickest way to farm harmony is to, er, farm it at your farm Get your Tillers rep up to the level you need to buy the songbell seeds and grow them every day. At exalted with them you'll have 16 plots and that's 1.6 Spirits of Harmony a day with no effort.

I don't know the recipe for success, but I know that the recipe for failure is trying to please everyone.

As for motes of harmony there is no magic in it, just kill anything that moves in Pandaria. Mobs in the Vale of Eternal blossoms have the best droprate overall, but as a tank I favor doing my farming in Dread Wastes.

While that is true, you should also look at killing time. If you can kill lower level mobs 2-4 times faster OR pull in larger groups- sometimes killing weaker mobs is a smarter idea. Hence why people farmed in Kun'Lai's caves until they basically gutted the drop rate there.